Friday, April 15, 2016

Not Your Daddy's Tyrannosaurus rex...

You may have already heard the chatterings, mumblings, and rumors spread hither and thither. In the smoky backroom chatboards, comments sections, forums, and discussion threads a growing disquiet over a certain very real - but also mytho-cultural - beast. To those attuned to the dinosaur blogosphere internet meta-brain this notion should be none too radical but to those uninitiated the notion is simple and revelatory at the same time: we might just be getting Tyrannosaurus rex totally wrong as goes appearance, especially in the face. T. rex might look just plain silly, or weird, or altogether more surreal than what we have built it up to look like.

Tyrannosaurus rex - as both a scientific and cultural phenomena - is imbued with both values as goes it's appearance. And humans - as culturally adapted critters - try as we might can not decouple the two as stringently as we might hope in reconstructing this beast.

This post is going to be necessarily both a cultural and scientific deconstruction of Tyrannosaurus rex facial appearance focusing on two main aspects. As such we must wear both a cultural and scientific hat here in an attempt to de-clutter and re-imagine a creature undeniably real but also imbued to an obscene degree by cultural baggage, gender notions, and aesthetics. This treatment will also hold implications for many other extinct theropods to greater or lesser degrees. Where you fall down in the end as goes appearance - will be a blend of science, aesthetics, and culture - which is as how it has always been with these guys (i.e. extinct animal restoration).

The beginning (and really the end as well we shall see) of T. rex facial reconstruction must really start at ground zero - the skull. Just take a second to breath it all in... it really is structurally and aesthetically a work of art and powerfully built symmetry.

AMNH 5027, A.E. Anderson Public Domain

Now as appealing as this bony synthesis of power and grace is we must concede that the bony appearance of an animal's skeletons is often times not a direct reflection of an animal's outer appearance. In T. rex the skull's beautiful, symmetric, and aesthetically pleasing appearance may have a lot more to do with being influenced by a uniquely and profoundly strong set of muscles than it being a true reading of it's life appearance. T. rex has evolved to deliver crushing bites and sustain stresses in multiple force vectors. It is built to give and take a licking and keep on ticking.

But just take a second to bathe in the below photos...

Red Tegu photos credit from Helen Zhu.

The above x-rays (borrowed from Helen Zhu's research page) should give you moment to pause and reflect upon how much soft tissue can surround and obscure even a reptiles skull (diapsids generally being impoverished in facial muscles compared to mammals). It should be noted that huge jowls of the red tegu are a male feature and are mainly for show although the huge pterygoideus muscles certainly help with cracking snails and shellfish - a common part of the animal's diet.

As the above youtuber puts it these prominent muscles in the tegu form some very voluptuous "neck boobs" on the side of the jaw. Crocodiles also feature said neck boobs that form the dominant jaw closing group of muscles in their particular jaw apparatus (they don't put a lot of muscles on the top of the head for concealment reasons).

Now to what extent and how much T. rex, and other tyrant lizards - or even theropods in general had prominent pterygoideus muscles is equivocal and loaded with uncertainty as is the muscular reconstruction of any extinct animal. But as one of the largest and in fact the strongest biting terrestrial vertebrate T. rex likely had some rather prominent "neck boobs", at least more so than is almost always depicted.

Here are some pics on how the pterygoideus muscles may have attached in T. rex and Majungasaurus:

Again this post is not so much about the bite force and the technical side of theropod / T. rex biting but appearance and the cultural conceits there of. So whether or not T. rex had red tegu sized "neck boobs" or maybe something like a croc or somewhat less than that - there is a lot of room for variation in how much "neck boob" you want to put on your T. rex as well as other theropods. But do we see this variation in T. rex paleoart? I can say almost universally nope, no we don't. Go peruse T. rex art and you will see that the pterygoideus is petite at best and sometimes not even there.

One avenue of looking into how much muscle T. rex was packing there is to compare the size of this muscle in juvenile versus adult crocodilians. As is seen in these dissections of immature crocs the size of the pterygoideus is fairly modest in relation to the animal's whole head. This changes with adulthood when we the grotesquely flared pterygoideus of large crocs.

Is this ontogenetic change due to a shift from small prey to large prey? I don't know if that is completely the answer... in fact I am not sure that adult crocs prey on animals any larger relative to their own size than baby crocs. I suspect it has a lot more to do with the ol' square cube law. As crocs get bigger their volume increases disproportionate to their surface area. Muscles have volume but they are also influenced a lot by surface area. Big crocs have to move a lot more mass (i.e. from having more volume) relative to small crocs and grow muscles disproportionately larger than small crocs to basically do the same job - bite and subdue prey. There is probably a paper or two in there somewhere but I don't know if it has been written.

Following from this maybe... just maybe... T. rex had to grow some quite impressive jaw closing pterygoideus muscles to do it's job amply - after all it was certainly no light weight.

Again my main point in all of this is not to convince you one way or the other if T. rex had red tegu sized neck boobs or something more moderate. Chances are it had something prominent there and given it's size and proclivity for a particularly strong, tenacious, and evenly distributed bite the pterygoideus would and should be apparent in life.

But do restorations give this muscle enough flare, weight, and voluptuous girth? I would say no and the reason I think it is underrepresented I suggest is cultural.

We have all been smitten, bedazzled, and suffered a bit of a man-crush on T. rex's hypermasculine and all too handsome jawline.

We are drawn to Tyrannosaurus rex - possibly on a subconscious level - because the skull encapsulates many of the male attributes we find desirable in our own species both sexually and for our leaders, warriors, and mythical superheroes.

And I did not even mention the strong chin of T. rex which adds a whole other layer to the hypermasculine attributes we are drawn to in the T. rex skull.

But what if the strong jawline of T. rex - seemingly chiseled out of tooth, scale, and hypermasculine hero worship - was cloaked by layers of feather, flaps of skin, or as suggested earlier in the post by particularly voluptuous "neck boobs" and jowels giving the animal a decidedly softer, rounder and perhaps feminized appearance? Things could change a lot as goes appearance. The skull of T. rex is optimized for muscular performance, not to appeal to the cultural and sexual biases of extant hominins.

Astute readers should note that this cultural and anatomical analysis of T. rex appearance has implications for how other theropods are restored to greater or lesser extents it is just easier to make the point with big ol' sexy rexy.
For the next part of my analysis I want to talk about a soft tissue that regular readers of the dino-blogosphere should be well aware of and which is quite possibly one of the most contentious issues in theropod soft tissue restoration: lips. Yep, I am going into lips.

To summarize my views going in and add some arguments that probably need reiteration:

Theropods most likely had lips. I also think that these lips (contra most depictions including my own) would have mostly or even completely covered the teeth. While the notion of a croc like skin sheathing the head of theropods has been argued, probably most vociferously by Tracy Ford, what I find lacking is that fully exposed teeth and oral cavity would put a lot of burden on the animal in terms of water loss via exhalation. Here it is worth noting that terrestrial predators keep a pretty tight seal on the mouth. Aquatic animals, not so much - sharks and crocs come to mind but there are many more examples of exposed snaggle toothed aquatic animals. There definitely seems to be a bit of bias for aquatic animals having more exposed oral regions than terrestrial.

One of the critiques for lower lips in theropods is that the preserved skulls for many theropods suggest that the upper teeth would penetrate into the lower lips and gums of said animals cutting such features to shreds. Check these pics out. However one of the best rebuttals to this argument was done by Tyler Keillor in the chapter Jane in the Flesh: The State of Life-Reconstruction in Paleoart from the excellent book Tyrannosaurid Paleobiology. Let me quote Keillor directly as I don't know if this argument gets enough exposure:

What's my name? extreme jaw closure credit James St. John CC2.0

On Jaw Closure (pp 160-161):

"...fossilized theropod skulls have been found with the jaws tightly closed. While some artists have used this as the living animal's closed-mouth pose, I offer another interpretation. The jaws that are tightly clenched may show a postmortem deformation, akin to the "death curve" seen in the axial columns of many vertebrates under certain conditions. As tissues desiccated and shrank in the dead animal, the massive jaw closing muscles may have shortened and pulled the jaw tightly closed, more so than it would have been in life. Punctures in the palate of Sue occurred after death, when the jaw's dentary teeth were closed further than they had been in life (Brochu 2003). In skulls that are preserved right-side up and resting on their jaws, overlying sediment compaction after burial could further crush the jaws closed in dorsoventral compression (Bakker et al. 1988)"

I would actually go a little further than Bakker and suggest that irregardless of whether the skull is preserved right side up compression from multiple angles could compress the jaw shut. Why? Because the earth shifts and moves all the time not just from top to bottom.

Furthermore Keillor draws attention to a rather simple and seldom mentioned critique of the "extreme close mouthed" interpretation which is bone on bone contact with no room for soft tissue. When a skull was put in this pose (extreme close mouthed) Keillor noted "contact between the quadrate and angular, the jugal and extopterygoid come close to touching the surangular, and the dentary teeth contact the palatal bones and medial maxillae (pp 162)".

Keillor also decides that in the situation of tyrannosaur lips he must look beyond the extant phylogenetic bracket of modern birds and crocs due to their unique specializations (beaked and aquatic) not offering the ideal evolutionary context for a toothed terrestrial predator. And here I agree the EPB feels a little lacking. Keillor expands the bracket to consider large terrestrial predatory lizards i.e. the komodo dragon as the ideal model for looking at the type of "lippy" tissue present and the ideal neutral position of jaw closure. Essentially this lizard lip type arrangement allows a tight seal when closed - to enhance "sniffing" presumably - as well as protect the oral cavity and teeth from dehydration and abrasion. Yeah it is kind of a "just so" argument but keeping your cutlery sheathed and moist probably has some fairly obvious benefits to it in drying terrestrial environs full of abrasives.

Probably one of the best representative views of the lizard lips hypothesis is that done by the promising game Saurian. Picture below borrowed from said development team:

credit Saurian development team

You should note that when the mouth is open the upper teeth have nice little "pockets" to fit into between the dentary and outer lower lip. When the jaw is shut the lips seal things up nice and flush to create a tight seal that inhibits moisture loss and enhance the ability to suck up smells via the nose.

That the upper teeth went below and lateral to the dentary is corroborated by the path the nutrient foramen follow on the dentary.

Below one of my favorite skeletal mounts of T. rex because it eschews the overdone Rex vs Triceratops battle. You can see quite clearly how the nutrient foramen on the upper jaw come right to the edge of the alveolar margin on the upper jaw (maxillae). But if you trace the path of the nutrient foramen on the bottom jaw (dentary) you will notice that while the nutrient foramen come up against the edge of the teeth in the anterior and posterior they take a noticeable dip towards the middle of the jaw - which corresponds directly with where the longest teeth from the upper jaw would be presumably in closure.

note how nutrient foramen take a dip along bottom margin of jaw corresponding to longest upper teeth

So all is hunky dory right? T. rex - and probably most predatory theropods - had lizard lips fairly similar to monitor lizards like komodo dragons right?

Not so fast Mr. Lizard Lips...

To prime you for my argument please take a good long hard look at another readily available wiki pic of ol' sexy rexy that is taken from the front. If you look into its orbits and squint just a bit you will see it....

credit ScottRobertAnselmo CC3.0 "Sue"

There are some (blasphemy!!) very mammalian things going on here... those endearing forward facing eyes looking right into your soul... then there is the VERY prominent nasal region (smell being a noted mammalian sense)... that pinched in upper snout which allows the binocular vision... which itself creates a sort of "muzzle"... which terminates in some heterodont dentition with vaguely "incisiform" front teeth for nipping and the tallest but still very stout and almost caniform teeth midway back on the upper jaws... and that flared back of the skull creating a vaguely cheeky countenance. Not only are we attracted to ol' sexy rexy for it's ruggedly handsome jawline but, well, to put it frankly it is harkening up some distinctively mammal type sentiments in us that remind us vaguely of the mammal things we are ourselves and which we allow most intimately in our homes and lives.

Cave Bear. wiki commons

Furthermore when we look at terrestrial predators that share these same attributes of heterodont dentition, binocular vision, a dominant olfactory sensory apparatus - they don't have lizard lips, they have loose, draping, jowel like lips. Yes I am looking at canids, ursids, hyaenids, and even felids to an extent. And yes I took the liberty of extending the bracket further than reptiles to include these predators that might offer more utility than a lizard. Because really what we are talking about is simply growing more skin and all kinds of animals grow all types of skin so again here I don't think the EPB offers much utility. I can see why people are more comfortable with the lizard lips hypothesis for T. rex it might feel safer than what I am offering. But let's break that somewhat arbitrary rule and see where it takes us...

To clarify I should stipulate that I am not suggesting we consider muscular mammal style lips in T. rex and other theropods but basically loose and hangy jowls of flesh (think condor cheeks but not continuous across mouth).

What is lacking in the lips debate is really any type of analysis comparing the adaptive benefits of tight sealing lizard type lips versus the more open hanging mammalian style lips. That debate has not occurred because, well to put it bluntly, mammal type "bulldog" like lips in T. rex and other theropods has been shut down by not being talked about at all really. These are the assertions that essentially shut down the topic I hear and feel free to illuminate me if there are more rigorous reasons not to consider bulldog lips in the comments section btw.

"Too far outside the phylogenetic bracket"

- Well when we infer lizard lips we are already outside the phylogenetic bracket... so.... and it is a bit telling that many seem to have no problem inferring fleshy mammalian (albeit non-muscular) cheeks in ornithischians but how do dare you consider fleshy, hangy lips in a theropod!!

Or my favorite: "I find them unlikely"
- Like that is all you have to say on bulldog style lips to not consider them? No support at all for not considering, just saying "unlikely"...

I suspect that there is more to it than this and people don't want to consider bulldog style lips because well... aesthetically and culturally it is not what we might like or even feel comfortable with on theropods and especially ol' sexy rexy. Because as I have been saying all along these are as much cultural creations as they are objective scientific animals. Both academics and fans of theropods and T. rex have ignored the idea of hangy, floppy lips in these animals because... for the most part they just seem to laugh and ridicule the idea away.

So as opposed to trying to decipher the type and extent of "lip" in these animals via skeletal traces which I think is a proposal loaded with potential pitfalls - for example how do you account for the amount of stem cells that might just grow loads of skin and tissue (?) - I am going to take another line of inference. I will be exploring lizard lips versus jowl style hanging bulldog lips in terms of relative adaptive benefit. This is admittedly not going to seal the deal either way because there is some subjectivity involved as well as the fact that animals don't always evolve into "optimal" or "perfect" organisms. However I do think comparing the relative benefits of either style of lip in lieu of really being able to eliminate either possibility is a valid form of inquiry. Again it might not seal the deal but it may open up some minds to possibilities...

The Smell Situation

There is one important distinction between lizards and theropods/mammals. Lizards primarily scent the world via their Jacobson's organ - the vomeronasal organ. In all lizards and snakes this organ is present and in reptiles that scent their prey the distinctive fork tongue is the tool that is used to gather sensory input from the environment and put into contact with the vomeronasal organ. Lizards and snakes - because of this system of sensory input don't need loose lips to let information from the environment into their oral cavity because their forked tongue does all the work for them. For lizards and snakes having loose lips to let chemical cues into the oral region is redundant and an unnecessary potential source of water loss. It is true that certain mammals have this organ but in general it is substantially reduced compared to reptiles. I can find no reference to this organ in birds and crocs and it is likely absent or extremely reduced in dinosaurs.

However, as anyone who has had or watched a baby explore its environment via its mouth can attest, having a relatively open and exploratory labial region may carry significant adaptive advantage. Animals can taste things and loose lips that can be pressed into various substrates can help pick up and adhere odors that can then be picked up by the nose or tasted. Having loose jowl type lips in this scenario of helping to scent or taste things would hold substantial adaptive advantage over the tight sealing lizard lips associated with reptiles that explore the world via their fork tongue.

It is not unreasonable to argue such adaptive benefits to various theropods - especially T. rex - in scenting and tracking food, rivals, mates etc etc. The open jowls and additional sticky substrate exposed to the environment would help trap and collect scents in close proximity to the nose. Certainly a lot more potential adaptive benefits in these regards than thin closed lizard lips.

Hellhound Rex by Duane Nash

Tactile Input, Prey Handling & Delicate Nipping

Another benefit of having more open "bulldog" style lips versus closed lizard type lips is the potentially higher amount of sensory data collection points available to "feel out" things. This ability comes in handy in terms of how to react and fine tune grip/bite strength/position when engaged with struggling prey. Having lips that can sense and anticipate muscular twitches of struggling prey is a great advantage to have as it allows the predator to fine tune its own biting and avoid suffering undue injury. Lizard lips, exposing much less sensory surface area than bulldog type lips, offer less data collection points to make these rapid adjustments. Again, adaptive advantage goes to the bulldog lips.

I know that there is something about cats I should be saying here I read somewhere. That when biting struggling prey the sensitive lips and whiskers are able to detect and collect information on the prey. Ok found something I can give to you from The Other Saber-tooths: Scimitar tooth Cats of the Western Hemisphere:

from pp.26:

"large scale movement of the prey relative to the predator can be constrained by powerful forearms, but fine scale adjustments in upper canine placement require tactile input from whiskers, lips, and nerves in the periodontal ligament and pulp cavity."

Granted T. rex was probably not making the precise bite adjustments of a felid but still could be of use.

The "incisiform" front dentition which allows delicate scraping of meat off of bones is also potentially aided by exposed and extensive lippage. Having a bit of a blind spot here and lacking sensory tactile front paws T. rex could feel out where the trace bits of meat are on a bone and better position its incisors for delicate nipping. Thin and not too supple lizard lips would be less efficient in these regards. Or whiskers...

Take home point: precise biting/nipping with heterodont dentition is associated with loose lips in extant animals and not lizard lips.

Teeth Baring

Although humans have bastardized this traditionally violent signal of aggression into something called a smile the ability to bare your teeth in a visible threat display is a potent and well understood universal across the animal kingdom. The lizard lip model might allow the teeth to show a little bit and maybe not at all in some theropods but in the bulldog lip model the upper teeth are potentially totally obscured ( I doubt that they had facial muscles to enact a sneer) but the bottom teeth and gums would be totally exposed when the theropod opened its mouth just slightly, creating a startling and disturbing visage of exposed gums and teeth. Once again, adaptive advantage goes to the bulldog lips.

Water Loss
Now you would thing that the tight fitting lizard lips would hold a substantial advantage over the more loose and draping habit of bulldog lips there might be more than meets the eye. Mucous could be particularly viscous inhibiting loss. The gap between the lower two mandibles forms a natural trough so that saliva would not be spilling out at a high rate anyways. And camels. Yes camels. If there was ever any animal that should be outfitted for water conversation among mammalia it is camels. Yet camels are noted for having particularly loose and jowly lips. And also, not coincidentally I suspect, camels are noted for a particularly good sense of smell. So whatever evolutionary disadvantages are incumbent upon having a loose set of lips in the dry desert they are not profound enough for camels to evolve a tight set of lips - or at least tighter fitting than the pics below attest.

credit AP

Tight Seal For Sniffing

Sort of a toss up. Reptiles with tight fitting lizard lips should get a pretty tight seal that will enhance sniffing. You would think that the more loose and drapey lips of mammal sniffers would be inferior but it does not seem to stymy them much as they seem to be doing just fine in terms of olfactory prowess. I don't see why such an arrangement in theropods would not work as well for sniffing.

Probably a mention of an extensive secondary palate in T. rex is worth mentioning here...

On a related note I did some research viewing of how bears - the penultimate scenters - actually do their sniffing. What I found was surprising and interesting and I don't know if it has been explored further. What I noticed is that sometimes when a bear is intently sniffing it will repeatedly open and close its mouth. Is it trying to taste the air? Or is it trying to suck air in closer to the nose by opening and closing it's mouth creating a vacuum. Check it out:

Check out the same sniff then open and close mouth behavior in this video as well:

And this brown bear does it too:

Anyways if the bears in these videos are trying to draw air into and closer to the nose I can easily imagine a T. rex doing a similar sort of behavior. Or maybe this behavior has something to do with a (reduced) Jacobson's organ?

Another interesting bear fact I learned in making this is that the lips of bears - apart from all other carnivorans - do not attach directly to the gums. Presumably this is to allow fine tune manipulation of small objects - such as plucking a single berry off a bush. Interesting to think how omnivory and the quest for high quality food items might engender "prehensile" appendages (I am looking at you ankylosaur tongues).

Anyways,

There is no terrestrial predatory tetrapod alive today that shares the suite of characteristics that T. rex has and which also has tightly sealing lizard lips. Asides from the vagaries of what can be gleaned from being one bracket closer on the subjective extant phylogenetic bracket in choosing the Komodo dragon as the best analog I would suggest that we look at the complete adaptive package of T. rex /tyrannosaurids and find the best and most comparable extant analog. Tyrannosaurus rex and other tyrannosaurids line up more closely with mammalian predators in terms of adaptive features including; a dominant nasal olfactory apparatus; heterodont dentition with precise "nipping" incisiform like front teeth; forward facing eyes; high metabolism; and an extensive secondary palate. I suggest that we have been more than a little hoodwinked by a serrated toothed, poisonous, scaly faced, fork tongued, and lizard lipped trickster in the Komodo dragon that fails compared to mammalian carnivorans in terms of nearly every metric listed when comparing tyrannosaurid facial anatomy, especially in terms of extraoral tissue (i.e. "lips").

Let the saliva spray!!

HorridRexDarkerSepia by Duane Nash

credit Carli Davidson

As I alluded to earlier in the post although I concentrated on T. rex this inquiry into lips may have implications for many theropods to varying degrees. Certainly I would hedge my bets towards more of the jowly type of lips in olfactory dominant tyrannosaurids and dromaeosaurids. There is room for nuance in many of the other lineages of theropods though; with variation ranging from more of the lizard type arrangement in some theropods up to this more jowly visage with all the various factors I mentioned in this post coming in to play: how important is scent? tactile prey handling or precision biting important? threat display important?

I also did not mention feathers in this post as this issue is taken up very well in this youtube video:

Feathers can be on top of skin, scales can be on top of skin but feathers and scales can not exist on top of one another.

And I am under no illusion that this post will overnight cause a whole scale reevaluation and overhaul in how we depict theropods. I fully expect most to adhere to the lizard's lip paradigm as that is what classic phylogenetic bracketing dictates. But in the end I find the lizard lips adaptation adaptively inferior to the bulldog lip adaptation. Ironically I have old images that still show lizard style lipped theropods which I still plan on using too... funny thing is I really wanted to concentrate on theropods other than T. rex but this is where my questions took me!!

Cheers!!

"A Long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defense of custom". Thomas Paine

76 comments:

Hi Duane.I don´t understand that large justification for your image. I understand that this is a ludic proposal of the T.rex appearance.And for me is enough. I understand that all of we that work with dinosaurs are trying to justify our drawings with the scientific intertextuality, but is´n always necessary. For me is a good drawing, very horrid, but I take as the freakish and disgusting side that nature also shows to us.

I only not sharing with your interpretation of the prominent chin in the Gurche´s painting, I always see in this picture the reference from a crocodile mandible, and I don´t see any chin. Maybe is a optical illusion. Gurche also paint a Daspletosaurus reconstruction and this time the mouth was covered with a prominent oral integument, specially in the inferior mandible.So, I consider unfair that interpretation of Sue´s painting.

Yeah maybe the chin in the Gurch image is shrouded in shadows a bit but the jawline is still very prominent. And there are loads of other examples of T. rex art emphasizing the chin.

I am not sure about your other comments. If you can be more specific on, I think you say my proposal is ludicrous? Well I kind of expected that kind of subjective response... if you have more meat behind this critique I would be very attentive to discuss further.

Hello!I remembered the Zilla ( Tristar,1998) movie, this was a big chin too.I don´t think that T.rex Jawline was inspired by the human body, but I like your representation of ageing in this fossil.If I will try to draw a Old Tyrannosaurus, I will take your advice. Specially with the "neck boobs" ( I don´t like the name, I see them like a sort of dewlaps)However, I agree that Humanization does a real influence in our representations of the past too.I don´t think that your proposal was ludicrous. I see it as a ludical, as a playful, manner. And it´s fine for me.

I've thought about things like this myself, although in a much more limited way, so I'm not too opposed to the ideas. Me, I wondered why, even in then-bleeding-edge GSP illustrations (popularised by them, even) there was a lizard-like lip right to the back of the jaw, connecting to a contour at the back of the skull (running round the quadrate or quadratojugal) while the corner of the mouth in birds rarely goes much further back than the front end of the jugal. It seemed to me that the downward dip of the jugal in a lot of non-avian theropods is a good point to place a fleshy little mini-jowl! I imagined vultures and condors, among others, as references or analogues - which is partly why I enjoyed your earlier posts about choanal grinding, too. Maybe I'm also going too far to one end of the PGB. I dunno.

However, turning art critic (just so you really love me) I think you've gone a bit heavy in your drawings here. The lips on your tyrannosaurs seem even looser and droopier than the lips of the bloodhound, an animal artificially (unnaturally?) selected to have looser lips and jowls than just about anything else! If other canids, and condors, and bears (oh my) are your examples of wild loose-lipped predators or carnivores, I think they could be just a little tighter.

I enjoy your reconstructions, especially anticipating them at the bottom of posts like this. ("Ooh, how's he gonna do this one?") As someone else said recently, I think your recent spinosaurs look much more plausible than the usual shrink-wrapped 'slasher pose' offerings. (Even when the latter do have tiny legs) I think you do a great job representing the kind of inherent symmetry or 'elegance' in features like thick/rolling skin, wattles, warts, spikes and spines, and other things that would usually put an animal in the traditionally 'ugly' bracket. But I have to say I'm missing a lot of it here. It's not giving me pleasure, schadenfreude or otherwise, to say that.I understand if you're trying to move a goalpost and extend a palaeoart sliding scale, as you said here, but I wonder if this depiction's a little sensationalistic.

Or maybe the soulless minions of orthodoxy have caught up with me. A little sensationalism is partly why I come here. Keep up the good work, will not be cancelling subscription just yet, etc. etc. ;)

And now that you and Pablo mention it, in my other/overlapping interest of speczoo and creature design, I see more dragons and other reptilian monsters with big, jutting, masculine chins. It does look as if Tristar Zilla's children spread far and wide.

Great post - an interesting idea and refreshing to read about. I tried to go for a "bulldog" appearance in this painting but didn't go the whole way like you have done. I think I chickened out and didn't want it to look too different in the end!

Very good post. Quite thought provoking, while I'm generally quite opposed to comparing the morphology of non-avian Dinosaurs with that of mammals it is certainly not all that far out, and that's besides the fact that there are quite a lot of birds with lose, feahterless skin.

Hi Duane, really nice post! Although I started reading with some skepticism, I agree in regards of the muscular structure, and also how useful is having some sort of lips (even more when your hands aren't that helpful to deal with food).I get chills when I saw the drawing of side view because less than a year ago I drew a picture that somehow meets with all the features!Cheers!

OOOk then, well I do not agree entirely, but I do agree with the lizard lips depictions. The drawing with the side view of a t.rex seems likely (except of the lip dangling upper jaw), though I would advise to put some more feathers on the head, not too many, but something like a griffin vulture and lips somewhat like a wolf or bear, not something like a domesticated dog. But once again, amazing post.

Followed every argument without any doubts arising. I once stood in front of a Museum of the Rockies' rex mount, on a raised platform where I could look eye-to-eye with (Sue? Stan? I forget). From that moment, I have seen Rex as wayyyyyyyy past mammalian in vision and everything else. Coincidentally I met Jack Horner on that very day for the first time. Anyway, you have nailed it time and again in this post. Congratulations Duane.

Bears and wolves seem to be a better analogue to T.rex than domesticated dogs in terms of facial disposition. After all, bulldogs were bred to hold onto prey, while T.rex would kill its prey with a single bite to the neck or back, and also, in a bulldog skull, the lower jaw is longer than the upper jaw. I do not mean to say you are completely wrong, since T.rex probably had somewhat mobile lips that looked like the lips of a wolf or bear, but not of a bulldog or bloodhound.

@Pablo Lara I assume zilla is Godzilla... oh yeah it did have a prominent chin.

@Warren JB Hey of course I shoot for the extreme!! Yeah as I probably mentioned on my face biting theropod post or Concavenator post what is the truth? Umm probably somewhere in between... sensationalistic maybe a little, but my rebuttal is King Vultures!!

@Alex L hey good painting but yeah I can see that you were thinking about going full bulldog but not quite.

@babehunter1324 thanks.

@paleomanuel good pic I like the eyes.. very alien looking.

@The eurypterid Well like I said in this post this will not seal the deal on theropod soft tissue anatomy and really nothing will save a perfect mummification. I don't think it applies to pterosaurs although I have heard murmurs that land crocs likely had "lips".

@D-man Yes that is a valid critique and I will probably hear more of " is an artificially bred dog a good model?" critique. But yeah I do push things to the extreme sometimes as I mentioned earlier. But on the other hand... since T. rex and theropods did not have muscular lips that can move around and explore the environment like mammals do maybe to compensate for this lack of exploratory capacity they were a little more loose and jangly. Sort of turning the whole oral mouth region into a sensory unit. Also - as several others have asked me what about those lips and face biting? Maybe the skin cells were a bit on overdrive due to the fact that they were getting bit and abraded pretty often. Sort of like fingernails that just keep growing... also keep in mind in the head shake pic they are stretching out of place due to the movement.

Ah, I see, though I still criticize their "janglyness", and yes, sometimes your hypothesis can take an "extreme" turn like the whole Concavenator spines. I guess we will never know until we find a T.rex mummy. Also I was thinking of drawing a T.rex wit somewhat mammalian lips like how Alex L drew with some Bearded Vulture elements in it. Also when I looked at your face bitting theropods post, I saw you say that the exceptions to the bald faced raptors would animals that lived in cold climates, well Dakotaraptor lived in an environment that was around 7-11 degrees celsius, sound the same temperature as the Yixian Formation with all those feathered dinosaurs with feathered heads. But nonetheless, this post is amazing and like you said in the Spinosaurus post, this post will make me think about many modern depictions of meat eating dinosaurs.

Also, for the fact that you said that they could not move their lips around like mammals so they compensated this with long jangly lips, I have a hypothesis on how they could do this: whiskers. Since many modern day birds have whiskers around their beaks, and since Kulindadromeus proved that feathers were ancestral to dinosaurs as sensory organs, maybe theropods retained this feature and it was eventually inherited by birds. After all if we look at a cat, dog, horse, Humpback whale, or rat skull, they do not show any evidence of whispers, yet they had them, so maybe T.rex and other theropods had this. I would love to hear your thoughts on this, meanwhile, I am going to draw a Concavenator and Baryonyx fighting over a carcass.

@anaonymous 7-11 degrees celsius are you sure? where did you get that number? Hell Creek was full of palmettos and swamp cypress, gulf coast plants that grow in the subtropics. There was for sure a winter chill, maybe some freak snows once in a while but I doubt those numbers. There were crocs, palms, and just too many plants we know today from fairly warm climates.

@ D-man careful with saying Kulinadromeus proves feathers are ancestral to dinosaurs or that the structures are sensory organs - have not heard that one yet? They could be analogous structures that evolved independently. I am skeptical of the feathers first hypothesis because it does not explain the lack of feathers in sauropods and hadrosaurs which we have excellent skin impressions of both and embryological remains of sauropods without any feathers. Why would they have had them and lost them when no birds have lost feathers in evolution?

What's not to like in this post? I mean, seriously, i always found the notion theropods didn't have "lips" quite tacky. I guess many people (both professionals and not) still like Rexy & pals with all their fangs proudly exposed for more psychological than scientific reasons, as (if i remember well) Jamie Headden said once.Anyway, it's good to know i'm not the only one who imagined tyrannosaurs with "mammal-like" lips; it looks strange at first because, i think, we tend to identify dinosaurs with reptiles and so on but, the more you look at a T.rex skull, the more you see there was probably more than just an almost identical replica of a lizard smile goin' on there... By the way, that's an idea i had for some time now (probably wrong, but still...), do you think the grooves we see on the sides of many theropods maxillae could have been, instead of the proof of hardened or cornified skin, the signs of the muscles which, when the animal was alive, made him/her move the lips? Could some dinosaurs have really had some sort of facial musculature afterall?

@Alessio Glad you liked it. I find it ironic that people all too readily accept cheeky ornithischians but giving big lips to theropods how dare you!! I have never looked at the grooves closely in those regards of suggesting muscles - is there anything on this?

Duane, sorry if for the Anonymous text about Hell Creek's temperature.

I got this number from the Saurian project's blog and the video shown above. It stated that it was around 7-11 degrees celsius, though there were some volcanoes littered around probably making it a bit warmer. I can't seem to find anything about the plants, but as for the crocs, the modern Chinese alligator can survive in sub freezing temperatures during the winters of China.

"Careful in saying that Kulindadromeus proves that feathers were ancestral to dinosaurs or as sensory organs"When I mean by feathers, I mean stage 1 feathers or the relative term "quills" so not true feathers, but feather like structures. I would think that prosauropods had some "feathers", but have lost the during their time and that they probably either never preserved with the animal or they lost them very quickly after they were born, like ho baby dolphins loose their hairs a few minutes after they are born. As for the sensory organs, Trey the Explainer has a neat informative video talking about which dinosaurs had feathers: "CM Kosemen and several scientists believe that feathers first evolved as sensory organs similar to whiskers"(7.06 min).

Also about the neck boobies, although the tegu has large neck boobies, all other monsters seem to lack this or the muscles were substantially smaller and this probably because tegu's don't have serrated teeth, and crocs seem to also have neck boobies and also have no serrated teeth. T.rex probably did not have such giant neck boobies since a other carnivores with powerful bites and have somewhat serrated teeth (tigers, jaguars, sharks, dogs, and non-Tegu monitor lizards). Instead of proposing T.rex had these, maybe predators that do not have serrated teeth such as pliosaurs since they are basically giant crocs with flippers, and I already have a picture of this thing in my head, and maybe Spinosaurus also had these neck boobies since it hd reduced serrations and attacked large fish, so maybe it had these neck muscles that helped deliver powerful bite and once it has its prey, the claws can then do the hardwork.

Also, I have never seen a mammalian lipped ornithischian, could you post an image of one.

Sorry, Duane, as far as i know there's no mention of it in the scientific literature... The general idea is that those grooves imply hardened skin, and in some cases i must admit it could work (i'm mainly thinking about abelisaurs, the bony texture of their jaws is quite different from the other theropods and instead reminds me of alligator skulls), but regarding tyrannosaurs and other "classic" sharpteeth like allosaurs and such, well, i'm pretty sure it was a different story...

Yeah saurian might want to 2x check that. The flora is highly consistent with a relatively balmy Louisiana/Gulf Coast feel. Maybe a little more north in Alberta it was chillier.

@D-man yeas finally someone asks about the brainy looking infoldings on the neck actually... they are completely 100% made up!! I wanted to create a novel thickened skin structure that would allow the neck to move and bend but offer some resistance to bites from rival rexes. The idea is that a glancing strike and the teeth bounce off kinda or a more deliberate grip and the folded skin is just wrenched away. Sort of inspired by black vulture skin.

"what did they look like on a real T. rex?" that is the point. It had them, they were probably substantial, however in art they are underrepresented or not even there. Why? I suggest people are attracted to the aesthetics of the jawline for socio-sexual reasons (reminds of strong male jawline).

Alessio thanks for looking. I have been less than impressed with efforts to correlate features on the bone to soft tissue features. But then again gives a lot more to play with.

The 7-11 degrees celsius was taken by paleontologists by studying the leaves of the native plants. They came up with a mean temperature of ~7-11 degrees celsius. The cretaceous was also under a cooling period.

Yeah that paper shows some cooling of sea surface temperatures in the late Maastrichtian not a cooling of the whole of the Cretaceous which is very far from the what was generally a very hot house world. I still can't find anything from saurian or elsewhere corroborating that 7-11 degrees celsius which is 44.6-51.8 fahrenheit, pretty darn chilly for palmetto palms and swamp cypress in fact pretty much out of their temperature range. Funny thing is I see that mean plastered in other places on the interwebs... I find it very suspect. Everything I read on the saurian page is going with a balmy Gulf coast temperature range for Hell Creek.

Pliosaur neck boobs? To tell you the truth I don't know if I have ever seen a good pliosaur skull muscular reconstruction. You should bug Max Hawthorne about them though...

@ D-man that is very interesting but I have my doubts chiefly because Cretaceous mid to high latitudes had a unique combination of sub-tropical and tropical plants combined with periods of low level light. That mean annual temperature just seems to low to support cypress, redwoods, crocs something else... something unique is going on and I suspect it has a lot to do with the unique and combination of periods of low light but generally mild and subtropical temperature...

@ Robert Haan "stuff of nightmares" thank you that means i am doing my job!! My take on albertosaurine tyrannosaurs in terms of what? flappy lips? well the benefits I conferred to T. rex in terms of big drooping lips can also be applied to most theropods to greater or lesser extents I guess.

It was probably something like a cloud forest. Since cloud forests have many sub-tropical to tropical plants and animals, and temperatures can range between 8-20 degrees celsius (Hell Creek is in that range), I suspect the climate would be something like a cloud forest. As for all the tropical plants you listed, I found out that redwoods live in temperatures as low as 40 degrees celsius, and I also found out that although the swamp cypress grow best in humid climate, adult cypress can actually tolerate the cold and low humidity. The reason why they are not as common as in the south is not because it is too cold, but it is because of specific breeding habits, in which ice prevents regeneration, but since it was not cold enough for ice in Hell Creek, they could still survive year round. I already explained that the Chinese Alligator can tolerate freezing conditions during the winter by either lying dormant in its burrow or staying in the lake and forming a breathing hole while the ice forms around it. Since again, it was too cold for ice, the crocodilians such as Borealosuchus and Brachychampsa could probably stay active all year round.

Right but if the mean is 7-11 degrees celsius that implies an average: there are days that are lower than the 7-11 degrees and days that are higher. If we look at modern US states at either end of that range in mean temperature they are Idaho at 6.9 celsius and Illinois at 11.0 degrees celsius average. It snows heavy in both of those states with many days below that average (mean) temperature. Palm trees and swamp cypress do not grow there. https://www.currentresults.com/Weather/US/average-annual-state-temperatures.php

I have seen redwoods in snowy conditions, I have lived in redwood habitat. There is a big difference between occasional chilly days in the 40's and even light frosts and a year round average of the temperature you are citing. If redwoods could thrive at those temperatures they would grow right up into Alaska but actually barely penetrate into southern Oregon.

Cloud forests are a special and unique places that require elevation and constant moisture. Hell Creek was at sea level and seasonal and not at all congruent with a cloud forest.

The paper you mention is specific to just one locality (the PDM) and not the whole of the Hell Creek formation. It also looks like they found just 17 leaf morphotypes to test - which is not a very high number statistically to test for paleoclimate using the leaf margin analysis.

But I did find another reference to a mean temperature of 10 degrees celsius in the lower Hell Creek... but then it got very much warmer to tropical like conditions in the higher (youngest) Hell Creek with a mean of 23 degrees celsius and full of palms. So maybe we are both right? From Encyclopedia of Dinosaurs chapter on Hell Creek

Guess we are. Also, I love these kind of arguments I do with you, and may I propose a 3 hypotheses.

1. When I read about Gigantoraptor, I wanted to know were it fits in the food chain. Suprisingly, I found out that it was the biggest animal in the region 84 million years ago, and since the tyrannosaurs their were around the size of a horse (Alectrosaurus), I was thinking that Gigantoraptor would have been the master scavenger in the region, basically chasing Alectrosaurus of its kills since Alectrosaurus was the size of a horse while Gigantoraptor was the size of an elephant (not as heavy though). I was thinking that Gigantoraptor would have had those waddles of skin like a vulture, similar to this...http://cdn1.arkive.org/media/6D/6D789619-9C9F-4BB2-842F-18DBDBBA2CCA/Presentation.Large/Lappet-faced-vulture-.jpg

2. I was also thinking that raptors would have been the dinosaur equivalent of big cats. Since the largest, (with the exception of Austroraptor) acting like tigers or leopards, in which they jump out of a tree or run form their cover and then get personal with their prey item, basically wrestling it to the ground, and then using those claws to stab into the throat. Tigers and leopards seem to be a good analogue to the giant raptors like Utahraptor, Achillobator, and Dakotaraptor.

3. And finally, I would like to propose the hypothesis of pelican pterosaurs. We have all seen Pteranodontids portrayed diving into the water like a pelican, but I'm thinking they had more in common. Since Pteranodontids like Pteranodon and Geosternbergia fill in the niches of pelicans, I was thinking that pteranodontids had this kind of neck pouch. After all, it would be helpful to scoop up extra fish with that mouth. I already have some sketches of the pteranodontids, Pteranodon, Geosternbergia, and Dawndraco with this pelican-like pouch, and who knows, maybe it ate more than fish with that mouthi.dailymail.co.uk/i/pix/2010/10/14/article-1320429-0B9BD05E000005DC-371_306x423jpg

1. I dunno maybe? I am kind of in the midst of my own work right now so I can't comment further.

2. Cats are unique. Not sure if I agree with this comparison in only the vaguest sort of way. I picture most large raptors as sort of a mash up of ground hawk, vulture, and hyena. More to come.

3. Nope. Pelicans have insane lower jaws that bow and flex when they impact the water. Pteranodon did not have this adaptation.

While I appreciate and am flattered that you seek my opinion on these topics there are loads of references you should be seeking on the web available to anyone before coming to me. I am going to have to start limiting my time answering off topic questions like this because they take away from the limited time (I have a full time job and do this in the spare time I can muster) I have to do the research, writing, and illustration for my own posts. So in the future if I can respectfully ask that you limit your comments and questions to things pertaining to the post at hand and not just dominate the thread with constant off topic posts and questions that would be much appreciated. Sorry if this sounds a little blunt or even rude but remember no one pays me for this and other researchers/bloggers are much less available than I am or even ask for money for answering questions or consulting. Cuz in the end this sort of feels like free consultation work. Thanks

Also, I probably came off a little like a prick dismissing those hypotheses so bluntly. That is something to get used to in any science field. I have to chuck and disregard a lot of my own pet hypotheses all the time. Get used to being wrong and while it is ok to be passionate don't take your own ideas to the heart. Read a lot of stuff and not just paleo or dinos. In fact this bit of a theropod kick I am on is due largely to the fact that I deliberately went away from them for a while and came back to them with new eyes.

But I do have to start limiting my time to on topic post related replies. Otherwise that is less time for writing new posts... and we all want new posts right?

Im glad to have come across this blog :)I find that commentary on our human projections super cool!

This particular topic is of much interest to me as my own reconstruction of Tyrannosaurus is based on mammalian jowls (I have been looking for that word for months!)

I first did a 3d reconstruction of the skull based on the latest ontogenic stage via the sue specimen (by "uncrushing" the skull into the plausible proportions) then added the hypothetical soft tissues. AFAIK the mounted Sue skull is an interpretation of the crushed skull.

One problem with using dogs as an analogy is that their substantial jowls and floppy tissues are a consequence of domestication. The degree isnt present in wolves for example but bears are a great analogy especially the idea of nipping and lower lip manipulation. One thing Id like to add to the discussion of soft tissue speculation is the trend in skulls with weak chins.Weak chins appear to give rise to increased fleshy lips in various animals. I have shared many of the observations made in the post when doing my reconstruction and are very plausible.

I have considered the "neck boobs" and am going to experiment with it in reconstruction.

Many mammals seem to have a vomeronasal organ and this also seems to be true for bears. They share an ancestry with dogs which have confirmed organs. It doesn't seem well studied but I found some investigation by a Benjamin Kilham into it so it does seem like they do to some degree at least, which would explain scenting the air with an open mouth. So not sure this translates well to Tyrannosaurus.

As for the particularly extensive lips and jowls...if you think it plausible that Tyrannosaurus has them for the sensory reasons you discuss, I'd be curious as to why other animals have not evolved something similar. Birds with solid beaks seem to be able to sense things with their mouths perfectly adequately without extensive fleshy lips, and the same holds true for crocodilians (no lips at all but need to deftly handle large prey) and lizards (the usual style lips we see for theropods). If large jowly lips make so much sense, why do other animals not seem to have them? Even mammals don't, certainly no wild mammal does to the extent the man-made breeds such as bloodhounds do. I think an investigation into all the downsides would be interesting. I suspect there must be plenty, as otherwise sure we would see such structures in wild animals also.

"Birds with solid beaks seem to be able to sense things with their mouths perfectly adequately without extensive fleshy lips" What are beaks and why did they evolve? Why do some lineages of animals always grow beaks and other not? What tissue did the beak replace or better yet what was the precursor tissue of a beak?

"I'd be curious as to why other animals have not evolved something similar" Other animals did evolve something similar they are called mammals. Don't get to caught up in the pictures they are mainly for shock and awe. Lippage on the order of wild canids, ursids, and hyaenas is quite adequate.

BTW you and nearly everyone else seems to gloss over the rather obvious point I make several times. Lizards have a tight sealing mouth because their tongue flicks in and out to sense their environment. Theropods (like mammals, birds, crocs) have no such tongue so a more "open" oral region would work better as an environmental swab than a closed one. Birds beaks are actually highly innervated and very tactile (what did a bird beak evolve from?....) crocs live and hunt in a liquid medium where their pressure pores sense changes in the watery medium they live in so no need for lips. Mammalian carnivorans need adequate lips to protect their enameled teeth as well as using their lip regions for tactile sensing of prey. Theropods likewise. Lizards simply do not provide an adaptive model for theropods.

I was rather caught up with the pictures, I'm afraid! I was definitely thinking of the bloodhound analogy more than wild mammals.

My main point with beaks was that fleshy lips don't seem strictly necessary for sufficient tactile sensation with the jaws. I suppose this would apply to lizards handling food/prey also? Mainly thinking of varanids of course (which do also make the effort to maneuver prey in the jaws). For that matter they might be a better example because beaks are an extension of the bones and teeth of the jaws. I suppose this is what you're getting at?

I absolutely know better about lizards using their tongue and am not sure why I said that, I definitely know varanids do it rather extensively. Do ALL lizards use their tongue for the majority of scenting? In species where scent really matters anyway. I know crocs are generally a poor example for this reason (I do wonder about the more terrestrial crocodilian species from the mesozoic era though, on a separate note), though crocs do often make their first strike and grab at prey above the waterline I suppose (relevant species of course)? Also mother crocs carefully handling nestlings on land must have good mouth sensitivity aside from the water based pressure pores to avoid harming them. And as for beaks, well, is there any chance that the simple flesh and skin around the mouth could be similarly innervated and tactile without being a hard bill?

I don't want to give too much away - as I am saving it for a future post - but I would double check any assumptions implicit in, "because beaks are an extension of the bones and teeth of the jaws". Yes it is true that the bones of the skull in birds reflect the shape and usage of the beak. There is definite reasons for this. But to assume that the beak came about as a reflection of the underlying bony tissue might be getting it backwards.

Something external to the skeletal system - a new way of feeding perhaps - incurred the changes that created a beak and then the underlying bony tissue was selected to optimize the mechanical workings of a beak. But some selective pressure had to have occurred that favored the evolution of beaks. And it did not happen just once in theropods but multiple times in flighted and non-flighted theropods.

Regarding lizards and especially monitors. Here we have a rather limited and not too precise analogy in the komodo dragon. The rest of the clan hardly counts as top predators being generalist small game, scavenging, egg eating - hardly the type of prey that could do you in. Because it is venomous it does not engage in prolonged skirmishes with large prey the komodo dragon is of limited utility in thinking about how the face and lips of a large terrestrial macropredatory animal handles bites. Mammalian predators offer much more insight because they actually bite and hold onto struggling prey. And in all cases their lips envelope the bite area and act as sensory input device. This is of adaptive benefit because it allows better sensing of where to place the bite and also gives a warning to predator if the prey is going to tense up and retaliate/shake etc etc. This torsional load could be disastrous to mammalian predators as this puts their canines in jeopardy. For theropods lateral torsion could hurt their teeth however they can grow in more. More importantly for theropods their entire skull is weak in the lateral realm full of fossa and thin struts of bone. Large lips would provide an early warning to lateral torsion that could shake off the bite and club the theropod laterally causing sinuses, fossa, and struts of bone to collapse.

The notion that theropods could simply walk up to and gouge out meter long swaths of flesh in fleeing, struggling herbivorous dinosaurs I don't take much stock in anymore. We are seeing more and more evidence that dinosaur skin was on a level of thickness in a class of its own. Literally an arms race of increasing thickness vs. increasing theropod biting ability.

Duane, i have to disagree strongly with this sentence: "Because it is venomous it does not engage in prolonged skirmishes with large prey the komodo dragon is of limited utility in thinking about how the face and lips of a large terrestrial macropredatory animal handles bites."

Komodo dragons will stay in prolonged skirmishes with struggling prey of similar size, at least thats what id say based on evidence:

"Komodo dragons naturally evolved to feed on 40 to 50-kilo prey animals like pigs and deer. When they feed on their natural sized prey, they kill 90 per cent of that prey in the first three or four hours. 75 per cent of the prey bleed out in the first 30 minutes and another 15 per cent continue bleeding and die within three or four hours."

"The primary Komodo dragon weapon is actually the teeth. They have these very flat, large, double-serrated teeth. When they bite, they bite and they pull straight back, so they leave parallel deep cuts. It is like with a saw, each cut follows the other one and each notch goes a little deeper. It is the same thing with their teeth. It is basically grip and rip. The mechanical damage alone from the teeth wounds is enough to kill in some cases. For example, on Rinca, where we do a lot of our research, an eight-year-old boy was killed there a couple of years ago. He went and squatted in the bushes and a big dragon came up, got him and cut right here (indicates). The dragon sliced right through the boy’s femoral artery. That mechanical damage, the tissue damage, is enough to kill. The blood spurt was about two metres from his leg. But it was a little unclear whether he died from that or from when the dragon then grabbed him mid-body and smashed his head against a tree. That caved in his head and the dragon ran off with the body while being chased by the family."

Sure, you can argue he talks about how prey can escape the initial attack and be weakened through blood loss after it, but based on the photos and videos i will argue that this isnt because the komodo dragon dont want to engage in a prolonged skirmishes, rather id argue the ideal situation for komodos is when prey dont run away, so that it can use its mouth and neck as a "can opener" of sorts.

Amazing post, but I have to disagree with on the fact of mammalian lips.

"Furthermore when we look at terrestrial predators that share these same attributes of heterodont dentition, binocular vision, a dominant olfactory sensory apparatus - they don't have lizard lips, they have loose, draping, jowel like lips."

Just because something has all these qualities does not mean that it has big jangly lips. Crocodiles have heterodont teeth, Boomslang snakes, dromeosaurids, and modern raptors have binocular vision, turkey vultures, german shepherds, sharks, and albatross have a great sense of smell, but they all don't have jangly lips.

"Too far outside the phylogenetic bracket"

Although this correct to some extent, you do have to realize that squamates are closer to dinosaurs than mammals are right?

As for ornithischian lips, as it turns out, they could have chewed perfectly well without lips. After all, lizards like Uromastyx do it and even if they had cheeks, they would not be mammalian cheeks, but rictal tissue.

And to top it all off, neither birds nor crocs have cheeks and osteological correlates to of mammalian-like fleshy lips is not present in dinosaurs.http://spinosaurus-the-fisher.tumblr.com/search/saurianhttp://www.tandfonline.com/toc/ujvp20/17/sup003http://www.tandfonline.com/toc/ujvp20/17/sup003#.V0OLfJMrJOwhttp://www.tandfonline.com/toc/ujvp20/18/sup003

Still a great post though (Totally agree with the neck boobs)

P.S. You may not get the full abstract for the last 3 links, but I posted them anyway because you may be able to access them.

@Pedro Bear fair enough on komodo dragon prey capture. I still maintain the vaguely incisor like dentition of tyrannosaurids would be aided by large lips that would "feel out" where the meat is on a bone, among other tactile uses that lizard lips simply don't provide to the same extent. A superior "environmental swab" that lizards simply don' need because their tongue does the trick of bringing sensory information into the oral region. Theropods would doubtless explore their world orally and an open and hanging "lip" region that exposes more surface area to sensory input is superior to the keratinized thin lizard lips that dominate our view.

@anonymous please consider leaving a name next time. We obviously differ on the suite of characteristics arguments. For me I would discount aquatic predators (sharks and crocs) because water is a medium that transmits vibrations well and negates the need for lips and birds don't have heterodont dentition or dentition at all for that matter. Furthermore their keratinized beaks negate the need for "lip" like structures that are necessary to keep enamel rich teeth healthy in a salivary juice broth. Tusks and croc teeth are actually fairly low in enamel and not very mineralized.

I happen to agree with ornithischians lacking cheek tissue having recently been swayed in this direction. Ironically the "rictal tissue" notion for what ornithischians had is exactly what I am implying for theropods. Take another look at my hellhound rex and you can see where I got the inspiration for that lip structure on the bottom jaw... people got a little caught up in the "mammal like lips" argument ( I never said that they were muscular) but instead are an extension of the rictal lining we see in birds today (albeit less keratinized). THey would do the same job that predatory mammal lips do but the exaptation is a little different.

Perhaps I wrote poorly, when I said that the beak is an extension of the underlying bone, I very much meant that it is more like lips than teeth. I'm not sure how to word this, but basically I was agreeing with you regarding beaks as not being a good example against lips because they are an unusual extension. As it were. Hence why I thought varanids might work better as an example.

Beak evolution...perhaps you're right, but I think this might also be overcomplicating it. I just think that perhaps since they are heavy, teeth are reduced in size as flight becomes more important. To compensate, the lips/mouth edges become more heavily keratinized as a substitute. Things go on from there. In herbivores, tough plant material rubbing the edges of the mouth encourages keratinization here also, which then becomes rather helpful in clipping the plants. Mammals have highly flexible lips compared to these herbivorous dinosaurs so they don't have the same problem. This is just a random idea though.

Varanids do hold onto struggling prey, even if it usually is smaller than themselves. Though I imagine the forces are usually rather low so moot point.

Since theropods had breakable, replaceable teeth, would excess lateral forces be transferred to the teeth which are then just broken, hence reducing the need for lateral skull strength? Or is that totally wrong? Complete theory, I'm not exactly a physicist. Physics. Does this also help varanids and crocodilians when it comes to dealing with forces from struggling prey?

Either way I think we can all agree that theropods would be taking something of a more tactical approach than just gouging their face into the nearest hide.

To Anonymous:I think some other lizards are also heterodont examples. Some varanids and tegus.

Depends which ornithischians you're discussing. I'm fairly certain that hadrosaurs, with those complex tooth batteries, were doing significant chewing and needed cheeks of some sort (Duane used condors as an example before I think, looks good to me). But others have dentition more akin to that of Uromastyx, though arguably these lizards don't chew a great diet, just bite the food as they swallow it. Not really chewing like we do, for example.

WHAT? Seriously, these statements do not make sense! Let's take a look: "There are some really mammalian things going on here" like foward facing eyes (let's forget about eagles, hawks and owls, for example), very proeminent nasal region (because vultures and kiwis find their food by using magic) and heterodont dentition (let's just forget that the teeth of a CROCODILE are longer and sharper when they are closer to the nostrils while those closer to the eyes are shorter and not as sharp as the front ones www.gettyimages.com/detail/pho…).

Also your comparatuon makes no sense: "Furthermore when we look at terrestrial predators that share these same attributes of heterodont dentition, binocular vision, a dominant olfactory sensory apparatus - they don't have lizard lips, they have loose, draping, jowel like lips" because all of them are MAMMALS, not non avian theropods for f*ck's sake! Also as we can see on my previous paragraph: eagles have foward facing eyes, but no muscular lips; vultures and kiwis use their excellent sense of smell to find food, but have no muscular lips; and crocodiles are heterodont, but are completely lipless. If these characteristics, while isolated from each other, have nothing to do with muscular lips, together they will still to not have anything to do with muscular lips. Also if you look at the bone texture in tyrannosaurus the facial area is rough and has numerous foramina. Because there is so many foramina there is no room for soft tissue to attach to. In all animals with muscular lips the bone texture is smooth. That is because they have soft tissue (muscle) rubbing against the bone. In theropods, the bone texture is rough, there are no muscles rubbing against it, therefore they lacked muscular lips.

Also by this logic of "this extinct animal had the X characteristic, and modern animals that show X also show Y but not Z, so this extinct animal surely showed Y but not Z" is proven to be nonsense if we look at ceratopsians and hadrosaurs: modern animals that show beaks have no cheeks so this would mean that these groups were cheekless, but they also had teeth clearely made to chew food (hadrosaurs had many tiny teeth placed close to each other that would, together, act like molars and triceratops, for example, had thick and somewhat pointy molars, not sharp and thin teeth like those of iguanas) and the shape of the jaw close to the teeth is very similar to what we see in modern cattle, what would mean that they had cheeks. So we see that the ratiocination showed on those paragraphs would indicate that ceratopsians and hadrosaurs would have cheeks and be cheekless at the same time (what is obiously a complete nonsense).

Also the fact that such lips would help to track scent while the animal hunted, because when the lips touched the ground they would bring scent with them and because the animal would be able to "taste" the smell, is nonsense because:

1- Even dogs that do not show very long lips, like german shepherds, are very efficient in tracking scent;

2- Dogs that show long lips like bloodhounds rarely open their mouths when tracking something unless they are tired and need to eliminate more heat trough the furless tissue of the mouth (also to keep the mouth open all the time like this would eliminate far more water than if it's mouth was lipless, or if it had small lips that only covered the gums, and closed, as only a small part of the upper jaw's gums would be exposed);

3- For such lips to take the scent on the ground efficiently they would need to touch the ground, but T. rex was BIPEDAL and would lose balance far easier than quadrupeds. So it would certainly not touch the ground with it's mouth.

And to end this: if T. rex had such long and hangy lips, they would caugh the attention of rivals during fights (as it would be a very soft and vulnerable part of the smout) and rivals would try to bite the lips off and we would gind clear tooth marks very close to the teeth and not only far from them, on the top pf the snouts.

I agree with basically all of your post, but If I have to land a small critique, I think you're comparing too much dinosaurs with today's mammals. Dinosaurs are birds so it makes sense to me that the T-rex could have had fleshy growths covering its face like a turkey's or a vulture have, and these structures could have formed lips because that could be an advantage, from an evolution point, but comparing these structures to a bulldog's lips I think it's kind of pushing it too far to be realistic.https://s-media-cache-ak0.pinimg.com/736x/d5/b9/60/d5b9608b4226438cea1b7fca542c2a8a.jpghttp://lafeber.com/vet/wp-content/uploads/dragoon_head-bodlina-wikimedia-labeled.jpg

I understand this is a rather old post, but the "T. rex with lips" controversy came up again in Carr et al. (2017):http://www.nature.com/articles/srep44942

The long-awaited descriptor of the upper Two Medicine Formation tyrannosaur Daspletosaurus horneri includes a brief but noticeable discussion on facial musculature, using birds and crocodilians as analogues. It is hypothesized that the density of neurovascular foramina along the lipline, particularly at the pointed rostrum, supported sensory integument similar to modern crocodilians, and not unlike Bob Bakker's early skin-wrapped "lizard lips" reconstructions. I think this conclusion is premature. While crocodilian-like mechanoreceptors were undoubtedly part of the tyrannosaur facial musculature, I have issue accepting the lipless reconstruction with the teeth sticking out; the organs may have been keratinized, and thus flamboyantly ornamented and colored. Even the article states that similar (if less extravagant and sophisitaced) foramina are present in "lipped" tetrapods such as cane toads and moles.

(Interestingly, the article also states that Daspletosaurus was to derived to be the ancestor of either Tarbosaurus or Tyrannosaurus. They all probably shared a more distant common ancestor in the form of Lythronax.)

Well Jason, I do not think he analyzed it properly. We can see it in the very beggining: he puts many skulls of different creatures there and says that just because all of them have rugose skull texture the comparation with crocodiles is not a great one, however he simply forgot that, even tough rugose texture can be caused by many things, it is obvious that different causes will lead to different textures on the skull (muscle attachment changes the surface of the bone, but the marke are clearely not the same as those of crocodylian keratinized skin). Therefore his first point does not stand.

He says that people like to compare T. rex with crocs because they are predatory, but this is simply not the case. We are talking about fossil data and accuracy, not a simple fan made comparation to make T. rex look cool.

And if the iregular texture of T. rex's skull was due to bites from rivals, the paleontologists would have realized it. The teeth have a specific shape and thanks to this it is easy for an authority in the subject to identify tooth marks left by a rival of it's own kind (that is how it was Discovered that Sue had a parasyte on her jaws when it died), but the texture found resembled that of a crocodylian skull. All of this without mentioning that:

- It was shown that the irregular surface goes almost all the way to the tooth row. It is nearly impossible for a T. rex to have had such an enormous area of it's snout bitten like that (just have the shape of the jaws in mind);

- D. horneri, just like D. torosus, had thin teeth designed for slashing and cutting. Such jaws would have NEVER left marks like those seen in T. rex.